The threats of old are still the dominant drivers of current species loss, indicates an analysis of IUCN Red List data by Sean Maxwell and colleagues.

Here we report an analysis of threat information gathered for more than 8,000 species. These data revealed a contrasting picture. We found that by far the biggest drivers of biodiversity decline are overexploitation (the harvesting of species from the wild at rates that cannot be compensated for by reproduction or regrowth) and agriculture (the production of food, fodder, fibre and fuel crops; livestock farming; aquaculture; and the cultivation of trees).

On the list

Since 2001, the categories and criteria of the IUCN Red List of Threatened Species — a standard for the evaluation of extinction risk — have guided assessments, now for 82,845 species. Assessors assign species to categories, including ‘near-threatened’, ‘vulnerable’, ‘endangered’ or ‘critically endangered’ depending on their population size; past, current and projected population trends; geographic range and other symptoms of extinction risk. Species in the latter three groups are collectively referred to as ‘threatened’.

To assess the relative prevalence of current hazards to biodiversity, we quantified threat information for 8,688 near-threatened or threatened species belonging to species groups in which all known species have been assessed (for complete list of taxa included, see Supplementary Information).

The basic message emerging from these data is that whatever the threat category or species group, overexploitation and agriculture have the greatest current impact on biodiversity (see ‘Big killers’).

Of the species listed as threatened or near-threatened, 72% (6,241) are being overexploited for commerce, recreation or subsistence.

The Sumatran rhinoceros (Dicerorhinus sumatrensis), Western gorilla (Gorilla gorilla) and Chinese pangolin (Manis pentadactyla, a scaly mammal), for instance, are all illegally hunted as a result of high market demand for their body parts and meat. These are just three of the more than 2,700 species affected by hunting or fishing, or by people collecting live specimens for the pet trade. At the same time, unsustainable logging is contributing to the decline of more than 4,000 forest-dependent species, such as the Bornean wren-babbler (Ptilocichla leucogrammica), India’s Nicobar shrew (Crocidura nicobarica), and the Myanmar snub-nosed monkey (Rhinopithecus strykeri).